FIYUORKSCKIN AND EOSIN
excess of alcohol, phenolphthalcin crystallises out in the form
of a white powder. Yield, 5 grams.
Properties.—White, granular, crystalline powder; m. p.
250 253° ; very slightly soluble in water, readily soluble in hot
alcohol ; soluble in alkalis with a crimson colour. See Appendix^
Fluorescein and Bosin,
Baeyer, Antmlen^ 1^76, 183, 3.
10 gnus, phthalie anhydride.
15 „ re.sorcinol.
7 „ zinc chloride (fused and powdered).
The phthalie anhydrkle and rcsorcinol are ground together
and heated in a deep tin dish or cylinder to 180". To the
fused mass the zinc chloride is added with continual stirring in
the course of ten minutes. The temperature is now raised to
210" and the heating continued until the mass is quite hard
(about 2 hours). On cooling, the melt is chipped out, pulverised,
and boiled for ten minutes with 150 c.c. water and 10 c.c. cone,
hydrochloric acid. The fluoresccin is filtered off, washed, and
boiled with a small quantity of absolute alcohol to dissolve
impurities. The residue is then dried on the water-bath. Yield
Eosin. — Fifteen grams of the fluorescein are mixed in a flask
with 80 c.c. spirit and ir c.c. bromine are dropped in from a
burette in the course of quarter of an hour. Heat is developed
and the fluorescein gradually dissolves until, when half the
bromine has been added, a clear solution is obtained. Further
addition of bromine precipitates the tetrabromo-compound